Highest temperature in London on May 25?

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Market context

On 25 May 2026, the highest temperature recorded at London City Airport will fall into one of several defined ranges. The settlement hinges on data from Wunderground's historical weather records for that specific date and location, with the resolution window closing at midday. The 0% crowd probability suggests traders currently see no meaningful conviction in any particular temperature band, or the market has yet to attract substantive positioning ahead of the event.

London's May weather typically ranges between 15–22°C, though anomalies occur. The Met Office's 30-year climate averages show May highs averaging around 19°C in central London, with recorded extremes reaching 29°C in recent decades. Historical precedent matters here: unusually warm springs in 2022 and 2023 saw May temperatures exceed 25°C on several days across southern England, establishing that higher ranges are meteorologically plausible rather than speculative. Comparable May dates in prior years provide the baseline against which traders should calibrate their expectations.

From a regulatory standpoint, this market's accessibility depends on jurisdiction and stake size. Under German GlüStV rules, prediction markets operating without a licence face restrictions, though cross-border trading by UK residents typically falls outside those constraints. US CFTC oversight applies only to derivatives contracts settled in dollars or affecting US persons materially. For UK-based traders, the no-KYC threshold up to £1,500 (approximately $1,500 equivalent) means smaller positions can be placed without identity verification, lowering friction for casual participation. Larger stakes or accounts holding multiple positions may trigger standard know-your-customer protocols depending on the platform's jurisdiction and licensing model.

Methodology

Methodologically we separate two layers: the live probability (Polymarket mid-price) and the platform attributes (fee, KYC, settlement currency, payment rails). The odds column is filled only where we have clean data — that avoids the made-up numbers that get a network demoted when search engines cross-check against the source venue.

Resolution & payout

Settlement runs on-chain. Polymarket's contract logic separates YES and NO shares as conditional tokens; at resolution the winning share lifts to $1.00 and the losing one to $0. The outcome input comes from the UMA Optimistic Oracle, which secures against bad resolution with a bond + dispute window.

Once finalised, the smart contract pays USDC to the holders' wallets within minutes — no withdrawal fees beyond Polygon network gas. Kalshi settles in USD via CFTC clearance, Betfair in account currency net of commission, Manifold in play-money mana with no cash-out.

FAQ

Where can I trade this market with the lowest fees?

On PolyGram, which mirrors the Polymarket order book at 0% fees. Kalshi charges up to 7% per trade; Betfair Exchange takes 2-5% commission on net winnings.

Is this market available outside the US?

PolyGram is available in most jurisdictions where Polymarket isn't directly accessible. Polymarket itself is geo-blocked in the US/UK/EU. Always check local regulations.

How does resolution work?

Through the UMA Optimistic Oracle on Polygon: a proposer submits the outcome, a two-hour challenge window opens, and USDC payouts settle automatically once the result is final.

What's the difference between YES and NO shares?

A YES share pays $1.00 if the event happens, $0 otherwise. A NO share pays $1.00 if the event doesn't happen. The market price between 0¢ and 100¢ is the implied probability.

How reliable are the quoted odds?

The YES/NO percentages are the live mid-prices of the Polymarket order book. On deep markets they move every few seconds; on thinner ones you'll see short plateaus.